Adherent Thin Films Research Articles

Single Step Electrosynthesis of Co-Ferrite Thin Films from Alkaline Non-Aqueous Bath

Electrosynthesis in a single step was used to obtain high-quality Co-ferrite thin films from an alkaline non-aqueous bath at room temperature. Several preparative parameters were optimized to obtain smooth and adherent Co-ferrite thin films. From XRD studies, cubic crystal formation was confirmed. IR studies confirmed spinel structure formation in Co-ferrite thin films. From SEM and AFM studies, smooth, uniform, and compact film formation was observed. From magnetic measurements, the value of saturation magnetization was (304 emu/cm3) obtained it is in good agreement with that of bulk value.

An investigation of chemical and electrochemical conversion of SILAR grown Mn3O4 into MnO2 thin films

Manganese oxide is an interesting material for electrochemical properties. It is well known that Mn3O4 (spinel) can be electrochemically converted to MnO2 (birnessite) via the electrochemical route during cyclic voltammetry (CV) cycling in aqueous Na2SO4 solution. Herein, the novel way is represented for the growth of highly adherent and compact Mn3O4 thin films by using successive ionic layer adsorption and reaction (SILAR) method. As grown Mn3O4 thin films are converted into MnO2 after chemical treatment by hydrochloric acid (HCl) via a disproportionate reaction. Mn3O4 thin films are converted into MnO2 by both chemical and electrochemical paths. During chemical conversion, at acidic pH, the crystal water insertion (H3O+) in Mn3O4 crystal provides the necessary driving force to transform it into MnO2 crystal. During electrochemical transformation, the specific capacitance was found to increase from 72 (1st CV cycle) to 393 F/g (1600th CV cycle). On the other hand, the specific capacitance was increased from 72 to 258 F/g through chemical transformation. Electrochemical and chemical conversion leads to ~5.5 and ~3.5 fold, respectively, improved supercapacitive performance than pristine Mn3O4 thin films. Both chemical and electrochemical conversion routes are extremely useful to recycle battery waste for supercapacitor applications.

Chemical Solution Deposition of Al(OH)3‐AlOOH Films: Application for Surface Sensitizing of Rigid and Flexible Substrates to Improve the Adhesion in Coating Technology Areas

AbstractIn this work, we present a simple and low cost formulation to obtain transparent Al(OH)3‐AlOOH thin films by chemical solution deposition at 60 °C. The deposited material was characterized by ultraviolet–visible spectroscopy, X‐ray photoelectron spectroscopy, and thermogravimetric analysis. The adhesion of the obtained thin films to various rigid and flexible substrates, that include tin‐free glass, polycarbonate, polymethyl methacrylate, cellulose acetate, polypropylene, polyethylene terephthalate, and polyimide, was tested. We also demonstrate here that a very thin film of Al(OH)3‐AlOOH can act as sensitizing layer for subsequent deposition of adherent and uniform CdS thin films on a variety of substrates; therefore, a modification of the reaction conditions by an increase in cadmium salt or a decrease in reaction temperature, which are factors that promote adhesion, is then not necessary. As a further result, a general formulation to deposit films of metal hydroxides/oxyhydroxides/oxides is presented. In addition, realistic assessments of X‐ray photoelectron spectroscopy and thermogravimetric analysis on Al(OH)3, AlOOH, and Al2O3 compounds are presented for the first time.

Development of an efficient electrochemical process for removing and separating soluble Pb(II) in aqueous solutions in presence of other heavy metals: Studies of key parameters

A very simple electrochemical process was developed for a high efficient elimination of Pb(II) from wastewaters. The principle is to remove soluble Pb(II) as oxide(s) adherent thin films only on the effect of an imposed specific potential by chronoamperometric method and an adequate pH, without adding reagents, at room temperature and in a conventional container. This treatment is very efficient for removing 99.99% of Pb(II) and directly reaching acceptable concentrations for the environment and drinking water standards, with low energy input. Firstly, the key parameters that could influence the efficiency of lead removal, such as the pH and the adequate values of potential, the initial concentration and the duration, were studied in pure water. Systematically, the solution was analyzed to quantify the concentration of Pb(II), and the recovered solid as an adherent thin film was characterized by X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) to determine its nature according to the experimental conditions. In a second part, the same treatment was applied with the optimized conditions in the presence of chemical ionic species and other heavy metals such as Cd(II), Ni(II) or Cu(II) to confirm the possibility to have a total elimination and separation of lead from these other heavy metals. To conclude, this electrochemical process was applied with success on an effluent coming from a wastewater treatment plant (WWTP), which confirms the real interest of this easy electrochemical process for an efficient separation and purification of wastewaters containing soluble lead.

Synthesis and characterization of aluminum dope zinc sulfide (Al:ZnS) thin films by chemical bath deposition techniques

A well adherent thin films of Aluminum doped zinc sulphide (Al:ZnS) has been deposited on silica glass substrates using acidic chemical bath deposition (CBD) containing zinc acetate, Aluminum Chloride, and thioacetamide. EDTA was used as complexing agent to control the free ion concentration of the thin films. Aluminum concentrations were doped by 2%, 4%, and 6% while keeping other deposition parameters constant as deposited Al:ZnS thin films. The samples were characterized by BrukerD8 diffractometer with cuKα (λ=1.5406A˚) radiation working at 40 mA and 40 kV, JOEL-2300 Analysis Station Scanning electron microscope (SEM), and Perkin Elmer Lambda 950 UV-vis/NIR spectrophotometer. The structural characterization of the samples show that no intense peaks were observed indicating the amorphous nature of the films. The surface morphology studies of as deposited Al:ZnS thin films shown the films were uniform, dense, and composed of spherical shaped grains. EDAX shows the elemental composition of Zn, S, and Al. The ratios of Zn/S in Stoichiometric even though the concentration of Aluminum is increased. Optical absorbance of the films decreased with increase Aluminum concentration. The large band gap makes them good materials for application as a window layer for solar cells.

Electrodeposited birnessite thin film: An efficient eco-friendly sorbent for removing heavy metals from water

Sorption is an efficient process for transferring heavy metals from polluted water to solid phase. Birnessite, which is a non-toxic layered manganese oxide, is particularly interesting for this objective due to its high sorption capacities towards heavy metals. In this paper, pure and nanostructured birnessite was synthesized as adherent thin films onto a solid substrate by electrochemistry with different characteristics for high sorption (e.g. mass, Average Oxidation States of Mn (AOS)). Sorption of lead (Pb (II)) and cadmium (Cd (II)) by these films was studied in terms of pH, ionic strength, sorption isotherm and kinetic order. The birnessite thin film with the highest AOS after synthesis (3.76) presents significant adsorption capacity for Pb (II) (538 mg-Pb/g) and Cd (II) (254 mg-Cd/g). A total decontamination at room temperature without filtration and energy input was obtained on model solutions and real effluents by increasing only the number of samples or the surface of electrodeposited birnessite on one sample. These birnessite thin films appear as very interesting eco-friendly sorbents for eliminating Pb (II) and Cd (II) from polluted aquatic media due to their easy synthesis and optimization process, and the possible reuses by efficient desorption in very low-cost conditions.

Development of atmospheric pressure glow discharge plasma assisted CVD system for the deposition of SiOx coatings

A novel, unique and self-designed radio frequency-based atmospheric pressure glow discharge plasma assisted chemical vapor deposition system (APGD-PACVD) has been developed indigenously for the deposition of SiOx coatings. The developed system has been evaluated for continuous, stable and low temperature plasma source for the deposition of adherent and uniform SiOx thin films on silicon substrates using a plasma of argon, helium and hexamethyldisiloxane (HMDSO) gases. The SiOx films deposited on silicon substrates were characterized by Fourier transform infrared spectroscopy (FTIR), field emmision scanning electron microscopy (FESEM) and energy dispersive x-ray analysis (EDXA) for confirmation of chemical structure of the coating. The results demonstrate the deposition of uniform and adherent SiOx films on silicon.

Investigation of the effect of Manganese doping in CdS nanocrystalline thin films

Undoped and Manganese (Mn) doped nanocrystalline cadmium sulphide (CdS) thin films were successfully grown onto indium tin oxide coated glass substrates using an aqueous wet chemical synthetic route. The effect of doping on the structural, optical and morphological properties was investigated using x-ray diffraction (XRD), Raman spectroscopy, Uv–Vis spectroscopy, photoluminescence and atomic force microscopy. XRD spectra revealed a single peak corresponding to (002) plane of hexagonal crystal structure of CdS. The shift in the peak position is also observed in doped samples confirming incorporation of Mn2+ ions into CdS crystal lattice. Photoluminescence emission bands were analyzed for the physical understanding of doping mechanism in CdS lattice.4T1 → 6A1 energy transition corresponding to emission band 550 nm is observed. The blue shift observed in absorption spectra in Mn doped sample indicates the decrease in particle size. Raman spectra exhibit two peaks corresponding to longitudinal optical phonon mode (LO) at 298 cm−1 and its overtone at 594 cm−1. Mn doped CdS sample shows red shift in the LO peaks representing incorporation of Mn2+ ions into CdS crystal lattice. The increased intensity of LO peak is associated to enhanced coupling between LO phonon and surface plasmon. Uniform, void free adherent nanocrystalline thin films were observed by atomic force microscopy.

A novel strategy to produce compact and adherent thin films of SnO2/TiO2 composites suitable for water splitting and pollutant degradation

SnO2/TiO2 composites have been widely studied as efficient photoanodes by various research groups around the globe. However, in this work, we display a novel and low cost strategy to synthesize thin films of such composites. According to the synthesizing strategy, various amounts of Degussa TiO2 P25 nanopowder ranging from 0.25 to 1.0 g were mixed to a fixed volume of SnO2 sol–gel solution. Then, the mixtures were spin-coated on doped tin oxide glass substrates. After a slow annealing at 500 °C, we obtained nanostructured SnO2/TiO2 composite thin films (CTFs). As-prepared CTFs were characterized by the scotch tape test, scanning electron microscope, X-ray diffraction and photoluminescence spectra. Furthermore, photoelectrochemical properties, photocatalytic activities and stability of all SnO2/TiO2 composite based PAs were studied. Results showed that composites with medium TiO2 amount exhibits more compact and adherent films than bare TiO2 films. We recorded an optimum situation for films prepared with 0.75 g of TiO2. It was proved that the SnO2 sol–gel method enabled compactness and adhesion of the processed composites. We correlated the photoluminescence intensity to the photocurrent density Jsc. The optimum Jsc, almost equal to 0.9 mA, was obtained in the case of 0.75 g amount of TiO2. This electrical performance is nearly nine times higher than that recorded with bare TiO2 photo-anodes. Moreover, replacing bare TiO2 photocatalyst by SnO2/TiO2 CTFs brought remarkable improvements to the photocatalytic degradation of methyl orange. Finally both morphological and mechanical properties of the composites were correlated to the stability and reusability of the CTF PAs.

Optical and microelectronic analysis of rhodamine B-based organic Schottky diode: a new trend application

The spin-coating technique was effectively used to prepare a good adherent and uniform thin films of rhodamine B (Rh.B). The investigation of the optical absorption revealed indirect energy gap of 2.1 eV and Urbach energy of 29 meV. The investigation of the electrical characteristics of the heterojunction-based Rh.B was achieved to extract the important parameters and identify the predominant conduction mechanism. Dark forward and reverse biasing current density–voltage characteristics showed notable rectification characteristics. The heterojunction conduction mechanism of Rh.B/p-Si confirms that observed mechanisms depend on the applied voltage range. The capacitance–voltage characteristics, measured at different signal frequencies, indicated the occurrence of an abrupt type of heterojunction. The frequency dependence of some heterojunction parameters like barrier height, maximum electric field, the width of the depletion region, and carrier concentration gives an indication for the type of interfacial layer of the heterojunction. A high dependence of the capacitance and conductance on both the biasing voltage and the applied frequency was observed. Moreover, the measured series resistance emphasizes the strong effect on the extracted parameters of the studied Schottky diode. Rh.B-based Schottky diode is a promising for multi-applications in an electronic device.

Effect of pH on the properties of electrochemically prepared ZnO thin films

Zinc Oxide (ZnO) thin films have been electrochemically deposited on fluorine doped tin oxide (FTO) coated glass substrates from an aqueous electrolyte. Deposition potential −0.96V was optimized by cyclic voltammetry experiment for slow scan rate 5mV/s with moderate agitation of electrolyte. The effect of pH on the electrodeposition of ZnO is studied by cyclic voltammetry, X-ray diffraction (XRD), scanning electron microscopy (SEM), optical spectroscopy and photoelectrochemical I-t transient characteristics. It is revealed that the pH of the electrolyte has significant influence on the surface morphology and structural properties. Highly crystalline ZnO layers with hexagonal crystal structure deposited for all pH of the solutions. A systematic shift observed in the reflections (002) and (101) is correlated with an effective tensile strain developed in the crystal lattice. A remarkable improvement in the crystallinity was noticed in the as-deposited ZnO samples with increasing pH and upon heat treatment. Optical direct band gap ~ 3.26–3.33eV and transmittance ~70 −80% was measured by optical spectroscopy. PL measurement showed the band edge emission at 375–382nm and a visible light emission at 410–550nm. The intensities of emission peaks are found to be affected by the pH of bath. The compact, densely packed and well adherent thin films of ZnO electrodeposited in zinc nitrate bath for pH 2.0, 3.5 and 6.0. The surface morphology has been changed from granular to disc shaped and finally a large hexagonal sheets were obtained with an increase in the pH of bath. Nearly stoichiometric ZnO thin films are electrodeposited at −0.96V versus Ag/AgCl reference electrode for pH 6.0. The photoelectrochemical (PEC) measurement (I-t transient curve) shows the enhancement in photocurrent with increasing the pH of zinc nitrate solution. After heat treatment the photocurrent is increased by 54%, 98% and 130% in the samples deposited from 2.0, 3.5 and 6.0pH of the bath. I-V measurements were further confirmed the current enhancement in all samples after heat treatment.

Effect of SiO2 interlayer on the properties of Al2 O3 thin films grown by plasma enhanced atomic layer deposition on 4H-SiC substrates

Al2O3 films were grown by plasma enhanced-atomic layer deposition (PE-ALD) on 4H-SiC substrates, with and without the presence of a thin SiO2 layer. The collected data indicated the formation of amorphous, adherent, and uniform Al2O3 thin films with a thickness of about 30 nm. The electrical characterization has been performed on metal–oxide–semiconductor (MOS) structures by both capacitance–voltage (C–V) and current–voltage (I–V) measurements. All these analyses demonstrated a better dielectric behavior of the Al2O3 film deposited on the SiO2/SiC stack, with respect to that deposited directly on the SiC substrate. In particular, higher dielectric constant value, lower leakage current density, and higher breakdown field have been found in the Al2O3/SiO2/SiC stack. Hence, it has been argued that the presence of the interfacial SiO2 provides a better condition for the growth of high quality Al2O3 films. In this context, the film density has been evaluated, and strong difference has been found in the density values, The correlation between the better electrical properties of the Al2O3 films on SiO2 and their higher density has been demonstrated. These results provide useful insights on the possible application of these Al2O3 films as gate insulator in 4H-SiC metal-oxide-semiconductor field effect transistors.

Cadmium Sulfide Thin Films Deposited onto MWCNT/Polysulfone Substrates by Chemical Bath Deposition

Cadmium sulfide (CdS) thin films were deposited by chemical bath deposition (CBD) onto polymeric composites with electric field-aligned multiwall carbon nanotubes (MWCNTs). MWCNT/polysulfone composites were prepared by dispersing low concentrations of MWCNTs within dissolved polysulfone (PSF). An alternating current electric field was “in situ” applied to align the MWCNTs within the dissolved polymer along the field direction until the solvent was evaporated. 80 μm thick solid MWCNT/PSF composites with an electrical conductivity 13 orders of magnitude higher than the conductivity of the neat PSF were obtained. The MWCNT/PSF composites were subsequently used as flexible substrates for the deposition of CdS thin films by CBD. Transparent and adherent CdS thin films with an average thickness of 475 nm were obtained. The values of the energy band gap, average grain size, rms roughness, crystalline structure, and preferential orientation of the CdS films deposited onto the polymeric substrate were very similar to the corresponding values of the CdS deposited onto glass (conventional substrate). These results show that the MWCNT/PSF composites with electric field-tailored MWCNTs represent a suitable option to be used as flexible conducting substrate for CdS thin films, which represents an important step towards the developing of flexible systems for photovoltaic applications.

Optimization of substrate-target distance for pulsed laser deposition of tungsten oxide thin films using Langmuir probe

The paper investigates the spatial and temporal variation of laser produced plasma of tungsten oxide using a Langmuir probe. The plasma was produced by laser ablation of tungsten oxide target using an Excimer laser of wavelength 248 nm. Our experimental studies confirmed that oxygen partial pressure (P) of 2× 10−2 mbar is sufficient enough to get stoichiometric tungsten oxide thin films and the plume dynamics was diagnosed for their spatial and temporal behaviour at the above optimised oxygen pressure. Spatial distribution was recorded with the target to substrate distance (D) ranging from the target position to a distance of 75 mm away from the target, whereas the temporal variation was taken in the range of 0–50 μ S with an interval of 0.5 μ S. The average electron densities were found to be maximum at 30 mm from the target position. However, ion density was constant beyond the probe distance of 45 mm from the target. The plasma current was found to be maximum at 28 μ S. The target to substrate distance was optimized for homogenous adherent good quality thin films using plasma parameters such as ion density and average electron density obtained at different oxygen pressure. The target distance and background gas pressure were correlated as PD scaling law and fitted as PD3 in the model.

Optimization of substrate-target distance for pulsed laser deposition of tungsten oxide thin films using Langmuir probe

The paper investigates the spatial and temporal variation of laser produced plasma of tungsten oxide using a Langmuir probe. The plasma was produced by laser ablation of tungsten oxide target using an Excimer laser of wavelength 248 nm. Our experimental studies confirmed that oxygen partial pressure (P) of 2× 10−2 mbar is sufficient enough to get stoichiometric tungsten oxide thin films and the plume dynamics was diagnosed for their spatial and temporal behaviour at the above optimised oxygen pressure. Spatial distribution was recorded with the target to substrate distance (D) ranging from the target position to a distance of 75 mm away from the target, whereas the temporal variation was taken in the range of 0–50 μ S with an interval of 0.5 μ S. The average electron densities were found to be maximum at 30 mm from the target position. However, ion density was constant beyond the probe distance of 45 mm from the target. The plasma current was found to be maximum at 28 μ S. The target to substrate distance was optimized for homogenous adherent good quality thin films using plasma parameters such as ion density and average electron density obtained at different oxygen pressure. The target distance and background gas pressure were correlated as PD scaling law and fitted as PD3 in the model.

Toward the control of thickness and uniformity in the coating of TiO2-P25 on glass

ABSTRACTThe deposition of TiO2-P25 on Pyrex glass is studied in order to propose a procedure for obtaining uniform and adherent thin films with a controlled thickness in the range between fractions of micrometer to a few tens of micrometers. Different deposition methods such as spray-coating, dip-coating, and drop-coating of liquid suspensions of TiO2-P25 powder are considered. The effects of pretreatment of the glass support, as well as postdeposition steps such as drying condition and thermal treatment, are also reported. A basic glass pretreatment and an acidic TiO2 suspension are chosen for an optimized adherence of the film. Drop-coating, associated with a slow drying under 55% relative humidity and a high-temperature thermal treatment is the method of choice to prepare coated glass slides in a large range of film thicknesses.

A simple chemical route for synthesis of microrods-like La2O3 thin films

The microrods-like La2O3 thin films are deposited on different substrates by using chemical bath deposition (CBD) route. The white colored, uniform and adherent La2O3 thin films are obtained after annealing at 823K. The La2O3 thin film is characterized for structural, morphological, optical absorption and wettability studies. The X-ray diffraction (XRD) pattern showed the polycrystalline nature of La2O3 thin film with hexagonal crystal structure. Formation of La2O3 compound is confirmed by Fourier transform infrared spectroscopy (FT-IR) study. The scanning electron microscopy (SEM) study showed three dimensional growth of La2O3 microrods.

Electrochemical template synthesis of adherent polyaniline thin films with tubular structure

The synthesis of nano and microstructured thin polyaniline (PANI) films by a simple and very efficient template-assisted method is presented. This work shows the synthesis and characterization of acoustically rigid thin films structured at nanotubular shape by using methyl orange (MO) as a template-assisted system. The amount of the tubes can be easily controlled by the charge passed. The morphology for different films growth was characterized by field emission scanning electron microscopy (FESEM), Atomic force microscopy (AFM), and quartz crystal microbalance with dissipation mode (QCM-D). Raman spectroscopy results show important changes in the conformational PANI chain of the tubular material compare with a non-tubular one that provokes the increase of bipolarons population. This should be responsible by some changes in the electrochemical behavior of tubular film compared with the granular material, due to the higher conductivity when the emeraldine form starts to be formed.

Synthesis and Characterization of PMMA Adherent ZnS thin Films by Spin Coating Method

Highly transparent and adherent ZnS thin films were grown on the glass substrate by spin coating method using an aqueous solution containing zinc sulfate and Polymethylmethacrylate in Tetrahedrafuran as a solvent. The films were characterized by X-ray diffraction, Scanning electron microscopy and UV-Vis spectroscopy techniques. The X-ray diffraction pattern shows the highest reflection peak at d=3.09Å (111). The diffraction angles and plane were (28.77) (111), (33.22) (200), (47.76) (220) and (56.62) (311) respectively. The particle size was found to be at around 35nm. The optical band gap values calculated for the film is 4.12eV. The UV- spectra reveal that films have low absorbance in the visible and near infrared regions. However the absorbance in the ultraviolet region is high. The enhanced absorption is observed in the neighborhood of λ=360nm. The SEM morphologies of the films revealed semispherical structure formed by the smaller particle on the ZnS film surface. Self-assembly of grains are observed in the AFM image of the film.

Nanocharacterization of titanium nitride thin films obtained by reactive magnetron sputtering

Titanium nitride thin films are used in applications such as tribological layers for cutting tools, coating of some medical devices (scalpel blades, prosthesis, implants etc.), sensors, electrodes for bioelectronics, microelectronics, diffusion barrier, bio-microelectromechanical systems (Bio-MEMS) and so on. This work is a comparative study concerning the influence of substrate temperature on some mechanical and tribological characteristics of titanium nitride thin films. The researched thin films were obtained by reactive magnetron sputtering method. The experiments employed two kinds of substrates: a steel substrate and a silicon one. The elaboration of titanium nitride thin films was done at two temperatures. First, the obtaining was realized when the substrates were at room temperature, and second, the obtaining was realized when the substrates were previously heated at 250 °C. The elaborated samples were then investigated by atomic force microscopy in order to establish their mechanical and tribological properties. The nanohardness, roughness, friction force are some of the determined characteristics. The results marked out that the substrate which was previously heated at 250 °C led to the obtaining of more adherent titanium nitride thin films than the substrate used at room temperature.